Guess Store Sandton poor quality products and assistance

My boyfriend purchased a Guess Chain from the Guess Store in Sandton City for me, Shockingly the chain changed colour within a few months despite me taking extremely good care of it. It is disappointing that you spend so much money on original products but they as good as counterfeit goods. I then reported the matter to the store and upon quality control I was offered a new chain however to date I have not received it. This complaint is going on for two months and no joy. I am disappointed with quality and customer service.